Vehicles each mounted with a power train referred to as a hybrid system formed of a combination of an internal combustion engine (e.g. the use of a known engine such as a petrol engine or a diesel engine is considered.) and an electric motor, have been developed and brought into practical use. Such a vehicle is mounted with electrical apparatuses, for example, a power storage mechanism such as a secondary battery or a capacitor for driving an electric motor used for traveling, and an apparatus for power conversion such as an inverter or a DC/DC converter. The secondary battery is charged and discharged through a chemical reaction that involves heat generation, and hence requires cooling. Furthermore, the inverter and the DC/DC converter have a power element that evolves heat, and hence requires cooling. Generally, an electrical apparatus requires cooling because when a current flows through a power line, Joule heat is generated.
Such an electrical apparatus may be placed, for example, between a vehicle rear seat and a luggage room. The electrical apparatus is placed in a duct-like casing that forms an air passage. A cooling fan generating a cooling airflow for cooling the electrical apparatus is placed between the electrical apparatus and the rear seat, on an intake air upstream side of the electrical apparatus in the casing. An upstream end portion of the casing is brought in communication with the vehicle interior (specifically, opens at a rear package tray), so that the electrical apparatus is cooled with air in the vehicle interior.
The inverter and the DC/DC converter may be integrated into an electrical apparatus referred to as a PCU (Power Control Unit), and mounted on the vehicle. The PCU may also be placed as an electrical apparatus between the vehicle rear seat and the luggage room.
A hybrid vehicle must be mounted with such an electrical apparatus along with an engine. Japanese Patent Laying-Open No. 2004-161058 discloses a battery cooling duct capable of reliably releasing a hydrogen gas or the like that may possibly be generated at a battery mounted on the vehicle to the outside of the vehicle. The battery cooling duct disclosed in this publication is applied to a vehicle mounted with a battery. The battery cooling duct includes a communicating passage that brings the battery in communication with a vehicle interior of the vehicle, and a gas retaining unit provided at the communicating passage.
With this battery duct, a hydrogen gas or the like generated at the battery can temporarily be stored in the gas retaining unit, and hence it is possible to reduce or prevent an entry of the gas into the vehicle interior.
Furthermore, Japanese Patent Laying-Open No. 2005-186868 discloses a cooling device for a power storage mechanism, capable of suppressing effects on an in-vehicle space and a pressure loss. The cooling device for the power storage mechanism disclosed in this publication includes an ejection unit that ejects air heated by heat exchange with the power storage mechanism from the power storage mechanism to the in-vehicle space, and an ejection fan that ejects the air heated by heat exchange from the in-vehicle space to the outside of the vehicle.
With the cooling device for the power storage mechanism, the air heated by heat exchange with the power storage mechanism is ejected from the power storage mechanism to the in-vehicle space. This air is then ejected from the in-vehicle space to the outside of the vehicle by the ejection fan. It is thereby possible to eject the air heated by heat exchange to the outside of the vehicle, without additionally providing an exhaust duct leading from the power storage mechanism to the outside of the vehicle and bypassing the in-vehicle space. Accordingly, it is possible to suppress effects on the in-vehicle space and a pressure loss.
In vehicles mounted with the devices disclosed in Japanese Patent Laying-Open No. 2004-161058 and Japanese Patent Laying-Open No. 2005-186868, if an electrical apparatus is mounted on a rear side of the vehicles and cooled with air in the vehicle interior, a cooling airflow intake port may be provided at the rear package tray.
However, if the intake port is provided at the rear package tray, the intake port is located in proximity to a rear windshield and irradiated with infrared rays of sunlight, causing a temperature rise of air in proximity to the intake port. Therefore, a temperature of the cooling airflow rises, and thus the electrical apparatus cannot efficiently be cooled.